Re: Lord D'Arcy and steam elevators

David Langford <ansible@xxxxxxxxx> wrote:

On Sun, 23 Apr 2006 10:29:27 +1200, zeborah@xxxxxxxxx (Zeborah) wrote:

My half-baked idea, written up in a brilliant sf short story in high
school(1), was that matter and anti-matter weren't created evenly
through the universe, so that as the universe expanded, while much
matter and anti-matter did cancel themselves out, some also formed into
like pockets. So we ended up with a matter galaxy (ours) and an
anti-matter galaxy (the one my starship arrived in, where it made
contact with a local planet, chatted happily for a while via EM signals,
and then attempted to land their starship. Bang. Oops.)

This isn't unlike the premise of Jack Williamson's 1940s "Seetee" stories,
which include the reverse situation of antimatter aliens whose starship
once travelled to our solar system. But the granularity is rather
different: there are antimatter asteroids in our own Belt, while even at
home the aliens had access to normal matter which they used for fuel.

Barring the idiocy of a spaceship reaching a distant galaxy but not
figuring out that everything around it is antimatter, is there any
reason why this couldn't happen to be true?

Martin Gardner's nonfiction =The Ambidextrous Universe= -- a good read in
any case -- seriously discusses the possibility of antimatter galaxies.
Maybe a 21st-century cosmologist would scoff, but others have thought it a
good enough idea for science fiction! However, there would be clues.

Haven't read it. (I have read the Larry Niven story.)

But to answer Zeborah's specific question, even with the hard vacuum
between galaxies, where matter and anti-matter galaxies were adjacent,
there'd be enough annihilation of electron-positron pairs to generate
a detectable amount of gamma radiation (at the right frequency).

It isn't there.

This doesn't mean the idea can't be used in an SF story, but if you
wanted to try and be consistent with current knowledge, you'd need to
invent some reason why we can't detect this annihilation radiation:
either it's blocked somehow, or something is stopping *any* mixing
even in intergalactic space.

I like the "parallel universes" approach myself -- matter and
anti-matter are created in equal amounts, but are not distributed
evenly between two or more parallel universes ... then someone
discovers hyperspace travel between distance galaxies, not realising
that *some* of the distance galaxies aren't in our universe ... :-)

Jonathan
.

Relevant Pages

  • The Gravitational Instability Theory on the Formation of the Universe
    ... Science knows the formation of matter in our universe was caused by ... RUFUS'S GALAXY WEB PAGE ... Basic Operation of Galaxies ...
    (sci.space.policy)
  • The Steady State Theory vs The Big Bang Theory
    ... Science knows the formation of matter in our universe was caused by ... RUFUS'S GALAXY WEB PAGE ... Basic Operation of Galaxies ...
    (sci.astro.amateur)
  • Re: Expansion and balloon analogy
    ... >> the original term was "recession of the galaxies. ... >universe that he fudged on his numbers to invent one. ... >>>explain the expansion process. ... Space is a medium for matter and if space is ...
    (sci.physics.relativity)
  • Re: The other direction
    ... Ordinary mostly luminous matter in galaxies ... the galaxies in the universe using the HST. ... Imagine an astronomer in that galaxy 13 billion years ...
    (sci.physics.relativity)
  • Re: Expansion and balloon analogy
    ... universe that he fudged on his numbers to invent one. ... >>the observations of galaxies moving away from each other. ... Space is a medium for matter and if space is ... filled with DM, then it is DM that is what is expanding and not space, ...
    (sci.physics.relativity)